The following U.S. patent applications which are herein incorporated by reference are commonly owned by the Assignee of the present application:    (1) U.S. patent application entitled Surgical Stapling Apparatus With Interlockable Firing System to Steven G. Hall et al., Ser. No. 12/031,326, filed Feb. 14, 2008, now U.S. Pat. No. 7,866,527;    (2) U.S. patent application entitled Articulatable Loading Units For Surgical Stapling and Cutting Instruments to Jerome R. Morgan et al., Ser. No. 12/031,001, filed Feb. 14, 2008, U.S. Patent Application Publication No. 2009/0206133;    (3) U.S. patent application entitled Surgical Stapling Apparatus With Reprocessible Handle Assembly to Kevin R. Doll et al., Ser. No. 12/030,980, filed Feb. 14, 2008, now U.S. Pat. No. 7,819,297;    (4) U.S. patent application entitled Surgical Stapling Apparatus With Articulatable Components to Kevin R. Doll et al., Ser. No. 12/031,066, filed Feb. 14, 2008, now U.S. Pat. No. 7,861,906;    (5) U.S. patent application entitled Surgical Stapling Apparatus With Control Features Operable With One Hand to Steven G. Hall et al., Ser. No. 12/031,030, filed Feb. 14, 2008, now U.S. Pat. No. 7,819,298;    (6) U.S. patent application entitled Surgical Stapling Apparatus With Retractable Firing Systems to Geoffrey C. Hueil et al., Ser. No. 12/030,974, filed Feb. 14, 2008, now U.S. Pat. No. 7,819,296.
Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument commonly includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil.
Different types of surgical staplers suitable for endoscopic applications are known. For example, one type of surgical stapler employs a staple cartridge. The staple cartridge typically supports a plurality of staples oriented on both sides of a longitudinally extending slot in the cartridge body that is adapted to receive a cutting member that is driven longitudinally therethrough. As the cutting member is driven through the cartridge slot, the staples are driven upward into the anvil portion of the instrument. The cutting member may be supported on a driven member that comprises a portion of the instrument apart from the cartridge. Examples of those types of devices are described in U.S. Pat. No. 6,905,057 to Jeffrey S. Swayze and Frederick E. Shelton, IV, entitled Surgical Stapling Instrument Incorporating a Firing Mechanism Having a Linked Rack Transmission and U.S. Pat. No. 7,083,075 to Jeffery S. Swayze, Frederick E. Shelton, IV, Kevin Ross Doll, and Douglas B. Hoffman entitled Multi-Stroke Mechanism With Automatic End of Stroke Retractions, the disclosures of which are herein incorporated by reference in their entireties.
Other types of surgical stapling instruments are configured to operate with disposable loading units (DLU's) that are constructed to support a cartridge and knife assembly therein. Such devices that are designed to accommodate DLU's purport to offer the advantage of a “fresh” knife blade for each firing of the instrument. An example of such surgical stapling instrument and DLU arrangement is disclosed in U.S. Pat. No. 5,865,361 to Milliman et al., the disclosure of which is herein incorporated by reference in its entirety.
Prior surgical stapling apparatuses, such as those disclosed in U.S. Pat. No. 5,865,361, suffer from the inability to be fired in thicker tissues (e.g., tissues with thicknesses greater than 3.5 mm) due to the increased loads applied to the firing system. Such increased loads can, for example, increase the likelihood that the firing system will fail when the knife is still in the anvil and may therefore require that the end effector be cut off of the tissue. Such failure mode can have serious patient injury consequences.
Thus, there is a need for a surgical stapling apparatus that is suited for use with disposable loading units that has an improved firing system configured to address the aforementioned problems.